ci: upgrade to codecov/codecov-action@v5 (#2842)

.github/actions/dart_package/action.yaml

@@ -84,7 +84,7 @@ runs:
       run: echo "package_name=${PACKAGE_PATH##*/}" >> $GITHUB_OUTPUT
 
     - name: 📊 Upload Coverage
-      uses: codecov/codecov-action@v3
+      uses: codecov/codecov-action@v5
       with:
         flags: ${{ steps.split.outputs.package_name }}
         token: ${{ inputs.codecov_token }}

.github/codecov.yml

@@ -11,12 +11,13 @@ coverage:
       default:
         target: 100%
 
-# Packages in third_party don't have 100% coverage, which shouldn't prevent
-# us from landing. Ideally, this would be configured to allow a non-100% base
-# and enforce that all changes have 100% coverage of affected lines.
 ignore:
+  # Ignore coverage for generated code (e.g. json_serializable).
+  - "**/**.g.dart"
+  # Packages in third_party don't have 100% coverage, which shouldn't prevent
+  # us from landing. Ideally, this would be configured to allow a non-100% base
+  # and enforce that all changes have 100% coverage of affected lines.
   - third_party
-  - lib/**.g.dart
 
 flag_management:
   default_rules: # the rules that will be followed for any flag added, generally